Field of the Invention
Embodiments of this invention relate to a hydraulic tool for oil and gas drilling operations, particularly, a torque wrench apparatus and method for making and breaking tubular joints in drill pipe strings.
Description of the Related Art
Hydraulic tongs have been employed in making and breaking joints in drilling pipe strings instead of manually-operated rig tongs to achieve a higher standard of safety and efficiency in the field of oil and gas drilling operations. However, because the torques generated during making and breaking of the joints are enormous, and the tool contacts corrosive chemicals in mud directly, it is important to introduce a torque wrench apparatus and method for making and breaking joints which is more rugged, more easily maintained, and causes less damage to the joints.
A number of hydraulic apparatuses for making and breaking joints in drill pipe strings are known. Typically, the apparatus is basically composed of an upper tongs, a lower tongs, a torque cylinder and a linkage installed between the upper tongs and the lower tongs. The torque cylinder is installed between the upper tongs and the lower tongs. Each tongs include a similar structure comprising a tongs block, two jaws, a number of dies, and two clamp cylinders. Dies are installed to the jaws, and each jaw is fixed to the rod end of each clamp cylinder, and the clamp cylinders are formed in the tongs block. In operation, the upper tongs clamp the upper joint while the lower tongs clamp the lower joint, and the torque cylinder extends to make up or retracts to break out the joints respectively, wherein the clamp cylinders are pushing the jaws toward the joints so that the teeth of the dies bite into the outer circumference of the joints.
However, the enormous torque generated during making and breaking joints requests an enormous biting force between the dies and the joints to avoid a slippage, and shock loads perpendicular to the rod of the clamp cylinders are usually generated also which may cause failure to the rod seals, and further, the enormous clamping force set for the maximum torque load is excessive for normal making and breaking joints excessively bites the joints. In short, such apparatuses have limited lifetime, are time consuming and difficult to maintain, and cause excessive damage to joints in drill pipe strings.